| | Glen Carbon, IL | Belleville, IL | United States |
| Population | 13,532 | 42,463 | 329,725,481 |
| Female Population | 50.0% | 52.3% | 50.5% |
| Male Population | 50.0% | 47.8% | 49.5% |
| Median Age | 40.5 | 37.6 | 38.4 |
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| Population - 2010 | 12,947 | 44,230 | 309,327,143 |
| Population - 2000 | 10,425 | 41,410 | 285,036,114 |
| Population - 1990 | 7,731 | 42,785 | 251,960,433 |
| Pop. 2000 to Now | 23.6% | -2.1% | 15.6% |
| Pop. 1990 to Now | 66.7% | -5.3% | 30.8% |
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| Population Density | 1,325.0 | 1,830.9 | 93.4 |
| Land Area | 10.2 | 23.2 | 3,531,905.4 |
| Water Area | 0.1 | 0.3 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Glen Carbon, IL | Belleville, IL | United States |
| Age 0 to 4 | 6.5% | 6.5% | 5.9% |
| Age 5 to 9 | 6.7% | 6.0% | 6.1% |
| Age 10 to 14 | 8.3% | 7.4% | 6.6% |
| Age 15 to 17 | 3.6% | 4.1% | 3.9% |
| Age 18 to 20 | 2.2% | 2.9% | 4.0% |
| Age 21 to 24 | 4.8% | 6.0% | 5.2% |
| Age 25 to 34 | 11.2% | 13.5% | 13.8% |
| Age 35 to 44 | 13.6% | 13.5% | 12.9% |
| Age 45 to 54 | 12.8% | 13.0% | 12.6% |
| Age 55 to 59 | 4.2% | 6.0% | 6.7% |
| Age 60 to 64 | 6.8% | 7.0% | 6.3% |
| Age 65 to 74 | 10.1% | 9.0% | 9.6% |
| Age 75 to 84 | 5.3% | 3.0% | 4.5% |
| Age 85 and over | 3.8% | 2.1% | 1.9% |
| space1 | | | |
| Race | | | |
| | Glen Carbon, IL | Belleville, IL | United States |
| White | 86.7% | 58.4% | 59.4% |
| Black | 4.3% | 31.3% | 12.2% |
| Asian | 1.6% | 0.5% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.1% | 0.2% |
| Other | 0.0% | 0.3% | 0.4% |
| Two or More Races | 3.8% | 6.0% | 3.2% |
| Hispanic | 3.6% | 3.5% | 18.4% |
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| Marriage & Family | | | |
| | Glen Carbon, IL | Belleville, IL | United States |
| Married Population | 53.7% | 40.5% | 49.8% |
| Currently Married | 52.4% | 38.0% | 48.0% |
| Married but Separated | 1.3% | 2.4% | 1.8% |
| Single Population | 46.3% | 59.5% | 50.2% |
| Never Married | 24.6% | 40.7% | 33.8% |
| Divorced | 13.2% | 13.2% | 10.8% |
| Widowed | 8.5% | 5.7% | 5.6% |
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| Household Size | 2.42 | 2.34 | 2.60 |
| Households | 5,539 | 17,589 | 124,010,992 |
| Family Households | 3,816 | 9,589 | 80,755,759 |
| Married couple, w/children | 34.0% | 26.2% | 30.5% |
| Married couple, no children | 38.5% | 37.9% | 42.9% |
| Non Family Households | 1,723 | 8,000 | 43,255,233 |
| Single householder, w/children | 17.5% | 25.9% | 15.8% |
| Single householder, no children | 10.0% | 10.1% | 10.8% |